1. Field of the Invention
The invention relates to a nonaqueous electrolyte battery, a battery pack using the nonaqueous electrolyte battery and a rechargeable vacuum cleaner.
2. Description of the Related Art
Use of a negative electrode active material with an average particle diameter of 1 μm or less for a nonaqueous electrolyte battery has been investigated. However, a negative electrode using the negative electrode active material is deficient in impregnating ability of the nonaqueous electrolyte since the negative electrode active material is compactly packed in the negative electrode, and may bring up a problem of deterioration of cycle performance.
JP-A 2004-119218 (KOKAI) and JP-A 2002-100354 (KOKAI) have reported that characteristics of respective active materials can be maximally exerted by using a mixture of a plurality of active materials having different average particle diameters from one another.
JP-A 2004-119218 (KOKAI) describes that discharge performance at a large load current can be improved by controlling the press density of large diameter particles and small diameter particles of lithium-cobalt composite oxide in the range of 2.8 to 3.2 g/cm3 and 2.7 to 3.2 g/cm3, respectively. The press density described in JP-A 2004-119218 (KOKAI) refers to an apparent press density obtained when a powder of the particles is compressed at a pressure of 0.3 t/cm2, and differs from a true density.
On the other hand, JP-A 2002-100354 (KOKAI) discloses controlling the proportion of the number of fine particles with a particle diameter of less than 1 μm in the range of 7 to 85% by pulverizing agglomerate lithium titanate obtained by a solid-solid reaction in order to improve discharge capacity and heavy drain discharge performance of the nonaqueous electrolyte secondary battery. In JP-A 2002-100354 (KOKAI), the true densities of the particles constituting the mixture are the same since the mixture of the particles with a particle diameter of less than 1 μm and the particles with a particle diameter of 1 μm or more is obtained by pulverization.